In refrigeration systems of the reverse cycle type, during operation on the heating cycle, a build-up of frost or ice may occur on the system outdoor coil with consequent impairment of system efficiency. To remove accumulated frost or ice from the outdoor coil, a defrost cycle operable to reverse refrigerant flow through the outdoor coil may be initiated. By this means, relatively hot gaseous refrigerant in the system is directed to the outdoor coil to melt frost or ice therefrom.
This build-up of frost or ice on the system outdoor coil during system operation on the heating cycle, and the reversal of the system to remove frost or ice therefrom through initiation of the defrost cycle reduces overall system efficiency. An increase therefore in the ability of the system, when operating in the defrost cycle, to effectively and rapidly remove accumulated frost or ice from the outdoor coil improves overall system efficiency.
In an outdoor coil having one or more rows of finned tubing in a substantially vertical plane, water present on the exterior surfaces of the tubing, for example, water resulting from defrosting of the outdoor coil, tends to pass in a downward direction toward the lower part of the outdoor coil. The tendency of water on the row or rows of finned tubing to move downwardly toward the lower part of the outdoor coil enhances the propensity of the lower part of the outdoor coil to form frost or ice and to accumulate the largest build-up of frost or ice during the system heating cycle operation. The downward flow of water or slush formed during defrost detracts from the melting process near the bottom portions of the outdoor coil.
With the above consideration in mind, it is a principal object of the present invention to provide, in an outdoor coil adapted for use in a reversible refrigeration system, an arrangement effective in directing during the defrost operation the relatively warm gaseous refrigerant to the lower extremities of the heat exchanger.
It is a further object of the invention to improve the ability of the reversible refrigeration system, when operating in the defrost cycle, to remove accumulated frost or ice from the system outdoor coil.
It is a still further object of the present invention to provide, in a reverse cycle refrigeration system, an arrangement operable to pass, during the system defrost cycle, relatively hot refrigerant gas directly to the area of the system outdoor coil normally having the heaviest frost or ice build-up.